This invention relates to a fluid handling apparatus especially useful in connection with a device for automatically analyzing a sample of a fluid under test.
In a clinical device for automatically analyzing a sample of a liquid fluid under test to determine the presence of various chemicals therein, such as the Automatic Clinical Analyzer sold by E. I. du Pont de Nemours and Company, it is necessary to provide a fluid handling system adapted to select various ones of a plurality of chemical reagents and convey a metered quantity of a selected one of the reagents to successive portions of the sample. The fluid handling system used in conjunction with the Automatic Clinical Analyzer includes a piston pump combined with a stack valve such as that disclosed and claimed in U.S. Pat. No. 4,002,070 (Howell), assigned to the assignee of the present invention.
It is necessary that the fluid handling system exhibit certain basic requirements. First, the system must be able to accurately meter precise quantities of reagent and accurately deliver the metered quantity to a desired location. The time required for reagent metering and delivery has an effect upon the operating cost, both from the standpoint of machine usage efficiency and from the standpoint of reagent supply expense. Second, in any fluid handling system, care must be exercised so that carry over of reagent does not occur. That is, caution should be exercised to insure that a reagent applied through the pump and valve to a given location is purged from the fluid handling system before a different reagent is metered and delivered. Unless this precaution is taken the possibility exists that the results of various ones of the tests may be impaired due to contamination of a given portion of the sample by chemical reagent utilized in connection with a test performed on a previous portion of the sample. It should be recognized that the same considerations of machine usage efficiency and purging fluid supply cost apply during a purging cycle as during a reagent delivery cycle.
A rotary valve is a device which is adapted to interconnect and to supply a fluid (either liquid or gas) from a single fluid source or from a plurality of fluid sources respectively to a plurality of user destinations or to a single user destination. Exemplary of a rotary valve are those devices disclosed in U.S. Pat. No. 3,752,167 (Makabe), U.S. Pat. No. 3,837,360 (Bubula), U.S. Pat. No. 3,542,071 (Lightner et al.), U.S. Pat. No. 3,443,592 (Felmlee), U.S. Pat. No. 3,237,644 (Beck et al.), U.S. Pat. No. 3,233,629 (Beck), U.S. Pat. No. 3,477,207 (Auger), U.S. Pat. No. 3,972,350 (Pickett) and U.S. Pat. No. 3,297,053 (McKinney). U.S. Pat. No. 3,474,784 (Wantz et al.), U.S. Pat. No. 3,995,494 (Muller et al.) and U.S. Pat. No. 3,124,162 (Cameron) disclose selector valve devices. Because of its ability to interconnect various fluid sources with various user locations a rotary slot valve may have utility in a fluid handling system for an automatic clinical analysis device. In addition, if the valve were configured to include a fluid metering chamber therein increased machine efficiency and reduced reagent usage would appear to be achievable.
A rotary slot valve generally includes a stationary stator member against the upper surface of which a valve seal member is rotatably disposed. Fluid communication between selected ones of fluid passages disposed in the stator is permitted through a slot provided in the rotating seal member while the other nonselected passages in the stator are isolated by the remainder of the seal member. However, as with any relatively moving contacting surfaces, friction and wear occurs. Thus, over a period of time it is possible that periodic replacement of the rotating seal member may be required. This activity requires a finite amount of time to accomplish and should be minimized in order to maximize machine usage efficiency.
In view of the foregoing it is believed advantageous to provide a fluid handling apparatus of the rotary slot type which is provided with a fluid metering chamber proximal to fluid passages provided therein. It is also believed advantageous to provide a positive displacement pump member movable within the metering chamber to draw fluid into the chamber and pump fluid therefrom. In addition, it is believed advantageous to provide a fluid handling apparatus of the rotary slot type in which the relatively moving rotary member may be expeditiously changed without the requirement of any tools to thus further maximize machine usage efficiency.